Cassini unveils Titan's surprising seasonal weather

Credit:ESA

This artist's impression shows changes in Titan's atmosphere before, during and after 2009.

NASA’s Cassini spacecraft has witnessed some of the most rapid and dramatic atmospheric changes ever recorded on Saturn’s largest moon Titan. New data from the spacelab provides conclusive evidence for the growth of a swirling vortex and a complete reversal in the direction of circulating air on the satellite.

In 2004, when Cassini began monitoring Titan, a vortex of atmospheric gas surrounded by a dense haze was visible high above the moon’s north pole, which was experiencing winter, as illustrated in the first and second globes in the above image.

When spring finally arrived in the northern hemisphere in August 2009, as seen in the third globe, the sudden change in temperature caused the direction of circulating air to reverse.

Within months of this reversal the sinking air had caused a vortex to form in the southern hemisphere, shown in the fourth globe. As winter continued, the vortex became far more prominent. This final stage can be seen on the fifth globe.

“Models have predicted this change in Titan’s atmospheric circulation for nearly 20 years, but Cassini has provided the first direct observations of it actually happening,” said Nicolas Altobelli, ESA’s Cassini project scientist.

Scientists were surprised to see such dramatic seasonal changes driven by solar activity on a world where sunlight is nearly a hundred times weaker than it is on Earth.

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